Leaking Tensioner?
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From: NYC
Leaking Tensioner?
i recently had my timing belt and water pump done at a porsche dealership. i paid premium prices. I was told later that the seal behind the tensioner wasn't replaced because it looked good. i feel that should of been a given, they should of done it, am i wrong?...i dont even think the tensioner boot was replaced. now i see some sweating from behind the tensioner. is the oil in the tensioner self contained or does it come from the engine? where is it leaking from????
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From: NYC
really looked like moisture, didn't look oily, but it was dirty..... like black water. I know my valve covers are leaking. im wondering if that leak(valve cover leak) is making its way down the front of the engine near the tensioner.
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From: Rochester, NY
There is a gasket behind the tensioner housing and some oil galleys back there to insure the oil in the tensioner is heated. Could be the tensioner gasket is leaking or they didn't torque the tensioner to the block correctly. Where are your cam covers leaking? I suppose it could drip down there, but there's a long way for it to get there. You're probably fine but keep an eye on it. If it gets worse, take it back to them and have them check it out since they did the work on it. Look through your receipt to to see if they replaced the tensioner gasket and oil.
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From: NYC
my cam covers are leaking mostly from the passenger side bottom, cant really tell if they are leaking from the front. So the oil from behind the tensioner is coming out of the tensioner itself, its not coming out of the engine block, which means the tensioner has its own specific oil....correct? thanks
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Chiod,
Yes, the tensioner has it's own oil. It is required for heat transfer to the internals of the tensioner. Leaking seems to be pretty common, although if they had the tensioner off, they should have rebuilt it which includes the boot, the internal O-ring, and the tensioner gasket.
The gasket is less than 10 bucks, but just replacing it doesn't ensure that it won't leak. Ask me how I know.
I'm pretty sure I've read that Mark Kibort runs his race car with no tensioner oil, and swears that it's not required, but many feel (like I do) that it is essential to the operation of the tensioner. There are two nipples on the front of the tensioner (in my car, and I'm pretty sure in all of them) that allow you to top it off or check it. One is to fill the other to drain/vent. I don't remember which is which, but if you go to the 928 international website you can link to some good tips/tricks for checking on and working on your tensioner.
Do some searches as well, this is a topic about which MUCH has been written.
Yes, the tensioner has it's own oil. It is required for heat transfer to the internals of the tensioner. Leaking seems to be pretty common, although if they had the tensioner off, they should have rebuilt it which includes the boot, the internal O-ring, and the tensioner gasket.
The gasket is less than 10 bucks, but just replacing it doesn't ensure that it won't leak. Ask me how I know.
I'm pretty sure I've read that Mark Kibort runs his race car with no tensioner oil, and swears that it's not required, but many feel (like I do) that it is essential to the operation of the tensioner. There are two nipples on the front of the tensioner (in my car, and I'm pretty sure in all of them) that allow you to top it off or check it. One is to fill the other to drain/vent. I don't remember which is which, but if you go to the 928 international website you can link to some good tips/tricks for checking on and working on your tensioner.
Do some searches as well, this is a topic about which MUCH has been written.
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From: Nova Scotia
There is ZERO oil pressure inside a tensioner - it operates basically on a gravity oil flow from captive oil in the tensioner body and a small reservoir (~30 cc) formed between the tensioner body and the block .... thusly the gasket. This gasket and/or the boot are the common leakers.
Remove the dist. cap and the right cam cover: spray the area down with a can of brake cleaner and an air hose .... and this will allow you to see where oil is originating.
Connect an oil ** can via plastic tube to the opened outside bleed screw (7mm), and slowly force oil into the tensioner until there is a clear flow out the more central bleeder. If it is already full, there was no leak .... etc.
** some get into a PMS moment debating on gear vs motor oil - both work fine IMHO.
Remove the dist. cap and the right cam cover: spray the area down with a can of brake cleaner and an air hose .... and this will allow you to see where oil is originating.
Connect an oil ** can via plastic tube to the opened outside bleed screw (7mm), and slowly force oil into the tensioner until there is a clear flow out the more central bleeder. If it is already full, there was no leak .... etc.
** some get into a PMS moment debating on gear vs motor oil - both work fine IMHO.
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From: saratoga, ca
Yes, the holbert tensioner was leaking pretty bad, and now its just got whatever residual oil that hasnt leaked out.( several years now). Scots didnt have oil in it either as it was never even filled and i just took it completely apart to rebuild the engine, and it was in fine shape.
however, by design, it should have oil in it and it shouldnt leak out. if the shop pulled the tensioner and didnt change the gasket, then they should do the job again and fix the tensioner leak by replacing the gasket the right way!
Mk
however, by design, it should have oil in it and it shouldnt leak out. if the shop pulled the tensioner and didnt change the gasket, then they should do the job again and fix the tensioner leak by replacing the gasket the right way!
Mk
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DE-tensioner, Jim is right [edit]
Chiod: Most of us here do our own work b/c of experiences like yours. You may for other reasons want to keep a relationship w/this dealer, but if as you say you paid premium, more than $1500?, rebuilding the tensioner is part of the job or should be, especially if it is leaking. From your description, it is. They just did not want to mess with it. Having said that, we do know that many leak and many owners, live with it w/o castastrophic results. Tensioner will do its job of informing you of a loose belt situation w/less than perfect oil retension, if the electrical circuitry is intact. Perhaps they could have been more forthcoming with the actual situation and at least have checked to see if the wiring was correct and the ground circuit functioning, or maybe they don't know what we know. Searching here will provide a wealth of info on this and other questions what will inevitably arise on an older car like this.
Last edited by SteveG; Mar 23, 2007 at 01:20 PM.
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Once again I suggest that we call it a "detensioner" since once the tension is set with the bolt and the locknut is tightened the ONLY thing that the device can do is detension loosen the belt to compensate for the thermal expansion of the aluminum engine. The cupshaped bimetallic washers change shape when hot and loosen the belt SLIGHTLY . The oil helps transfer the heat and on later models with the inner rubber o-ring it helps control the flutter which ALWAYS happens on the loose none loaded span of the belt ( crank tensioner roller to passenger cam ) The actual tension on the loaded working part of the belt is constantly CHANGING as the crank pulley PULLS the belt around turning the oil pump compressing the valve springs turning the water pump compressing more valve springs . The detensioner works on the loose part of the belt much as you have a loose part of bicycle chain ALL the work happens on the tight side the "detensioner" is just picking up some of the slack . You measure the tension ONLY at TDC because of the constantly changing loads as the engine turns. So I submit that the correct name is detensioner ! And it is NOT oil fed dose NOT use oil to add tension, does not EVER get tighter and is NEVER the cause of timing belt "failure" though it is OFTEN blamed for other issues errors primarily because 911 tensioner failure is a real issue and well known !
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There are some cavities behind the (de 
)tensioner that are open, and get filled with gunk, and water. It could be cleaning water mixed with oil you're seeing, if it's true they did not remove the (de)tensioner to service it.
One bolt (closest to water pump) is drilled through into an oil drain galley from the heads. Oil can seep from this bolt if it is not sealed with Loctite, or silicone.
)tensioner that are open, and get filled with gunk, and water. It could be cleaning water mixed with oil you're seeing, if it's true they did not remove the (de)tensioner to service it.One bolt (closest to water pump) is drilled through into an oil drain galley from the heads. Oil can seep from this bolt if it is not sealed with Loctite, or silicone.
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From: NYC
boy do i feel better after reading all the responses. I thought a leaking tensioner was a critical issue. If it lost all its oil, then the belt would have no tension and then it would come off or something, at least thats what I thought. Still, i am very picky and stuff like that bothers me, especially since i am spending a lot to make this car as leak free as possible.......... Realgasket oil pan gasket, valve cover gaskets, water pump and gasket etc etc...thanks guys
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
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928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
